Journal of Virology, September 2006, p. 8289-8290, Vol. 80, No. 17
0022-538X/06/$08.00+0 doi:10.1128/JVI.01450-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
| SPOTLIGHT |
Articles of Significant Interest Selected from This Issue by the Editors
How Do APOBEC Proteins Inhibit Human Immunodeficiency Virus Type 1 Infection?Members of the APOBEC family of cytidine deaminases potently inhibit human immunodeficiency virus type 1 infection. Although the antiviral effect is usually associated with editing of reverse transcripts, Bishop et al. (p. 8450-8458) have used a series of chimeric APOBEC proteins to show that the extent of viral inhibition correlates closely with levels of reverse transcripts, rather than with the extent of mutation. These results suggest that APOBEC proteins suppress infection by reducing the levels of viral replication intermediates as well as by mutating them.
Insight into the Mechanisms of Reovirus-Induced Apoptosis
Reoviruses induce apoptosis during infection of tissue culture cells and murine myocardial and neural tissues. Early steps in the viral life cycle that include attachment and capsid disassembly are critical for apoptosis induction. However, viral factors responsible for apoptosis induction and the underlying mechanisms are unclear. Coffey et al. (p. 8422-8438) have found that reovirus capsid protein µl directly induces apoptosis of transfected cells and localizes to mitochondria and endoplasmic reticulum (ER) in transfected and infected cells. Based on these findings, they propose that apoptosis is induced following virus membrane penetration by cytosolic delivery of a proapoptotic proteolytic fragment of µl that targets mitochondria and ER.
Marek's Disease Virus MicroRNAs Flank the meq Oncogene
MicroRNAs play important regulatory roles by targeting mRNAs for translational repression or cleavage. Several pathogenic herpesviruses encode microRNAs, which are proposed to function in viral latency and evasion of the host immune response. Using highly parallel pyrosequencing technology, Burnside et al. (p. 8778-8786) identified microRNAs encoded by Marek's disease virus (MDV), a lymphotropic alphaherpesvirus that causes aggressive T-cell lymphomas in chickens. Interestingly, the microRNAs cluster in two locations, flanking the meq oncogene and within the latency-associated transcript. Identification of the MDV-encoded microRNAs is a starting point for determining the molecular function of these intriguing molecules.
Host Gene Exploitation by African Swine Fever Virus
African swine fever virus (ASFV) is potentially a worldwide economic threat that produces a fatal acute hemorrhagic fever in domesticated pigs. Using an expressed sequence tag (EST) cDNA library, an antisense approach to randomly inactivate cellular genes, and a phenotypic selection strategy, Chang et al. (p. 8705-8717) identified host functions required for infection and propagation of ASFV. This work establishes the utility of EST-based functional screening in mammalian cells to discover host genes exploited by pathogenic viruses.
New Insights into the Replication of Prions
Prions are unconventional infectious agents composed of a misfolded conformer (PrPSc) of the native prion protein (PrPC). Once formed, PrPSc propagates itself by templating its conformation onto resident PrPC. The specific nature of the PrPSc-PrPC complex necessary for propagation is unknown. Norstrom and Mastrianni (p. 8521-8529) provide new evidence that the orientation of individual charged residues within the first of three 
-helices of PrP is critical for the efficient propagation of prions. This work suggests a previously unrecognized role for helix 1 in the process of prion replication that will help to refine current theoretical models of prion propagation.
Polyomavirus Makes Its Way Out of the Endoplasmic Reticulum
The murine polyomavirus (Py) enters cells by utilizing a retrograde transport pathway to the endoplasmic reticulum (ER) where it undergoes partial disassembly before exiting into the cytosol. Lilley et al. (p. 8739-8744) demonstrate that Derlin-2, a member of a family of ER membrane proteins involved in dislocation of misfolded proteins from the ER, is necessary for Py infection. The results indicate that Py utilizes this "quality control" machinery of the cell and a portal of exit normally used for elimination of protein waste.
Journal of Virology, September 2006, p. 8289-8290, Vol. 80, No. 17
0022-538X/06/$08.00+0 doi:10.1128/JVI.01450-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
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